Cheers...i reasoned that with a loom fire/short, by the time i stopped opened the bonnet and used a manual cut off it may be too late..With this its just flick a switch on the dash , couple of seconds at most

With the contacts held closed, it isn't such an issue, the thing that kills solenoids is switching high currents. I think it overkill though, you would be better improving the fusing arrangements in my opinion. That will also keep the important feeds like the clock and radio memories.